The Mormon pioneers were members of The Church of Jesus Christ of Latter-day Saints, also known as Latter-day Saints, who migrated across the United States from the Midwest to the Salt Lake Valley in what is today the U.S. state of Utah. The journey was taken by about 70,000 people beginning in April 1847, and the period is by convention among social scientists, assumed to have ended with the completion of the First Transcontinental Railroad in 1869. In fact, wagon train migration to the west continued sporadically until the 20th century, for not everyone could afford to uproot and transport a family by railroad, and the transcontinental railroad network only serviced limited main routes — one couldn't ask the engineer to take the train down the next five valleys; it went where the tracks led it.